These chapters covers everything you need to get started. If you are a developer, you can read all chapters, from 1 to 4. If you are more a web designer, then you probably only need to read chapter 3 to learn how to layout forms.
They've also been translated into French and can be found here. Content includes form creation, validation, Propel integration, nested forms, internationalization and some of the bundled widgets and validators that come with the framework.